The present invention relates to a rotary abrasive drilling bit for the purpose of boring the ground, which is devised to perform the drilling of the object face by constantly rubbing said face with the teeth equipped thereon.
An apparatus of this kind in the prior art, as exemplified in FIG. 1, is provided with a bit 101 which is constructed by planting a plurality of square cutting elements or chips 109 made of cemented tungstencarbide on a bit body 102 by arranging them so as to leave a desired interspace along the direction of circumference of said bit body and to let the edge of the respective chips slightly project from the top face of the bit body 102. In the case of an apparatus of such a construction, the length of a locus of the section of each chip 109 is more than about 5 millimeters and the sectional area of each chip 109 is relatively large as compared with the top face of the bit body 102, and there is admittedly caused no inconvenience in the initial stage of drilling work. However, when the edge of the respective chips 109 is worn down to become round with the progress of the drilling work, the boring efficiency lowers remarkably and at times the cutting operation comes to a halt. As a result, notwithstanding there still remains a sufficient portion of cemented tungstencarbide which constitutes the chips 109, the chips 109 must be replaced only because of abrasion of their edges. Accordingly, it has various disadvantages such that the work efficiency thereof is low and a large portion of cemented tungstencarbide is wasted without being fully utilized for the drilling.